1. Field of the Invention
The present invention relates to the technology of a display driver, and more particularly to a memory access method for a portrait display and a landscape display, and a display driver circuit.
2. Related Art
With the progress of the technology, mobile telephones become more and more popularized and have more and more functions. At present, the current mobile telephone starts to provide the digital television service. In order to satisfy the digital television specification, a portrait mode panel adopted in the conventional mobile telephone has to be changed to a landscape mode panel.
In order to utilize the resource effectively, one display driver integrated circuit is configured such that it can be applied to various panels. Taking the panels having the same resolution of 320×240 (Quarter Video Graphics Array, QVGA) as an example, the challenge induced when the same integrated circuit is applied to the portrait mode and the landscape mode panels is how to effectively apply the frame memory embedded in the integrated circuit. The capacities of the frame memories for the portrait mode and the landscape mode are the same, but the numbers of scan lines needed in one frame and the numbers of pixels needed on each scan line in the two modes are different. The portrait mode QVGA panel needs 320 scan lines, and 240 pixels are needed on each scan line. The landscape mode QVGA panel needs 240 scan lines, and 320 pixels are needed on each scan line.
Based on the display driver integrated circuit architecture, the frame memory is configured to satisfy the requirement of the resolution of the panel. If one QVGA panel needs 320 scan lines in the portrait mode, and each scan line needs 240 pixels, then the frame memory is configured to have 320 word lines each having 240×24 bit lines.
However, if the portrait mode display driver integrated circuit is applied to the landscape mode panel, the pixels on each word line of its internal frame memory are fewer than the 320 pixels required for a landscape display, and the lack of the required memory of 80 pixels on each word line of its internal frame memory will occur. Although the total capacity of the frame memory is kept unchanged, the number of pixels on each scan line is changed. Thus, the display driver integrated circuit cannot be simultaneously applied to the landscape mode panel and the portrait mode panel.